Hm, so I learned the hard way to be a bit more cautious about supported M.2 drives. I checked when I bought the ASRock board, but I wasn't nearly as leery with the ASUS board. My plan was to reuse a Samsung 850 EVO M.2 drive (SATA) with a Crucial M.2 drive (SATA) in the ASUS ROG Strix Z370-H Gaming, but it turns out that the board
only supports PCI-E M.2 drives in one of its slots. Fortunately, my 8700k system has a 960 EVO, which is the exact same size as the 850 EVO. So, I can just swap them and likely see no difference. I'd prefer the "better" drive to be in my main desktop, but it seems like a waste to spend the money on another PCI-E M.2 drive when I have something perfectly good lying around.
Although, it just came to me... if I want my main desktop to "have the best", my current i7-6700k desktop is using the 960 EVO 250GB drive as its OS drive too. If that slot supports SATA, I could steal that drive, and make some weird, convoluted mess of hard drive hot potato.
Man I thought they had forgotten to put it in the shop's box. I actually asked the courier to wait and I opened the box in front of him. Then I saw how tiny the 8600k's box was, lol. I had forgotten it comes without the cooler and some of the pics I had seen in reviews made it look huge.
Same thing happened to me when I had my processor shipped by itself. We're just so used to those lackluster stock coolers that we expect them to be there.
It looks like the CPU core voltage on auto was indeed the culprit: the motherboard was taking it up to 1.328V at load.
Do you have MCE (Multi-Core Enhancement) enabled? I remember reading that motherboards will jack up the voltage to support MCE, but I don't think the feature is fine-tuned enough to adjust the voltage dynamically if it's really needed or not.